View Full Version : low high-side pressure, help
mackking
06-06-2009, 04:02 AM
i am new to a/c but i am pretty knowledgable about it. i installed a brand new goodman 3ton heatpump split system, with matching down-draft air handler.
the lowest i can get the vent temp is between 59-62 degrease. the condensing unit came with a .073 orface, and the handler came with a .078.
i used the .073 first, but the temp was high, so i tried the .078 and it got better, but the pressures still wasnt right. 70psi on the low side and 155-165 on the high side. so i put in a .061 and the pressures to me were perfect, 70psi(low) and 240psi(high). i then tried a .082 and the pressures were off but the suction line was cold, but not cold enough. the suction line temp is 56 degrease and my vent temp is 57-59. so i know its not an air flow problem. and my hight side pressure is only 150psi. i also have little heat from the condenser and on the highside line. i have replace the suction line all the way, and checked the highside and found no restriction. me and my freind (wich has been doin this for years) are completely stumped. any ideas would be greatly appreciated. thanks
Magoo
06-06-2009, 04:18 AM
Initial thought is overfeeding evap., ie ., high suction / low discharge. the compressor current draw would be high. Basically banging its gumbs and going nowhere.
Do a system analysis as in heat in,heat out.
Could be airflow, could be expansion device. Think , system balance and start again.
magoo
ps .., talk SI and you will get better response from forum
Pressures are primarily a result of the temperature and volume of the air flowing through the coils. Orifice size has very little to do with it.
Pressures are meaningless if we don't know what refrigerant is in the system.
I'll take a wild guess and say R22?
mackking
06-06-2009, 08:56 PM
yes it is r22 sorry
Assuming you are charging to a particular suction line superheat, a smaller orifice will result in a higher subcooling. If the subcooling is too high, then liquid will back up into the condenser, driving up the high side pressure and that's a very bad thing. That's what happened with the .061 orifice. It is much too small.
You are trying to set up the system to match a pre-conceived notion of what you think the pressures and temperatures should be. It doesn't work that way.
All useful information comes from taking two temperatures and subtracting one from the other.
For just one example, the "condenser TD" is the saturated condensing temperature or SCT (from P/T chart) minus the ambient temperature. On a hot day the SCT (high side pressure) is higher. On a cool day it is lower. Whatsmore a high efficiency system will have a lower SCT (and TD) than a standard efficiency system, because the condenser coil has more surface area.
So, you can't tell if the high side pressure is right unless you also know the ambient temperature. And you also need to know the efficiency of the system.
And this is just for starters. There is a lot more to setting up a system than just a couple pressures and temperatures.
As a rough rule of thumb, we would expect the TD to be about 20-35F (SCT 20-35F above ambient). Light load being at the low end and heavy load at the high end. At the same time, higher efficiency would tend towards the low end while lower efficiency would tend towards the high end.
I have no idea what your outdoor temp was at the time you were testing the system, but let's guess about 70F. Your SCT should then be about 90-105F. On a P/T chart for R22, this translates to 168-211psi.
If the ambient was cooler, then this should be lower. If the ambient was warmer, then this should be higher.
I would start with the .078 orifice, and measure the air in/air out temps for both coils (temps close to the coils, not way out at the vents), the low and high side pressures, and the suction line (compressor inlet) and liquid line (condenser outlet) temps.
The temp at the thermostat would also be useful.
mackking
07-06-2009, 02:33 AM
ok lets see if i can give u everything u need. let me say thought that it doesnt seem to matter what the temp of the ambient is, the vent temp remains the same (56-58). but i try to keep the house at 70 and it will reach 76 in the heat of the day. the outside temp ranges from 78 in the morning to about 94 in the afternoon, with about 75 percent humidity. the suction line temp at the evaporator and at the condenser is 54-55. the hight side line temp ranges from 82-92, morning to afternoon. the unit is a 13seer. af far as your reference to high pressure, at 93 degrease outside temp, the pressure never gets above 165. and like i said, i know the .082 orface wasnt correct but it made the coldest air of all of the so i left it in there. i just replaced the unit because i originally installed a 3ton 13 seer air handler(new) with a 2 1/2 ton 10seer condensind unit(used). i had the exact same pressures and temps. i figured there was a problem with the used condensing unit so i changed it with this one. well that didnt fix it, so i changed the air handler(wich had a txv). and low and behold...same problem. i hope this info helps.
Magoo
07-06-2009, 03:05 AM
Over condensing.
The temp of the air in the room may not be the same as the temp of the air entering the air handler, and the temp of the air leaving the air handler may not be the same as the temp of the air at the vent. We need more accurate measurements closer to the coil.
... at 93 degrease outside temp, the pressure never gets above 165...
165psi gives you SCT of 88F. It is not possible for the SCT to be lower than the ambient. Your high side gauge is screwed.
If we can believe the low side gauge, which is uncertain at this point, then the SST is about 41F. The suction line is 55F, so 55 - 41 = 14F superheat, so we are picking up a heavy heat load with a fully activated coil. So why isn't it cooling your house? Either it isn't large enough to do the job or you are trying to cool the world (leaking and/or uninsulated ducts in hot areas?). Is this an attic unit?
Air in/out temps at the air handler will give us a better idea of what is going on with this.
mackking
07-06-2009, 07:32 PM
it would seem the you are basing my sct on line pressure and stating that its impossible. but my guages work fine, ive even used other sets. you sais yourself the you cant base temp on pressure. with a 92 degree ambient temp the high side pressure IS 165psi.
mackking
07-06-2009, 07:35 PM
my low side pressure is 70psi exactly no matter what the ambient temp is. witch is the correct pressure for the r22 to flash at 38 degrees. but its not, its flashing at 54 degrees.
Where do you have the high side gauge connected to the system?
it would seem the you are basing my sct on line pressure and stating that its impossible. but my guages work fine, ive even used other sets. you sais yourself the you cant base temp on pressure. with a 92 degree ambient temp the high side pressure IS 165psi.
This is just simply physically impossible. It cannot happen.
If the gauge is known to be accurate, then it is not sensing the pressure in the condenser. Which brings us to the gauge port.
... the hight side line temp ranges from 82-92, morning to afternoon...
The liquid line temperature cannot drop below ambient unless there is a restriction between the point at which the temperature is measured and the condenser.
If there is a restriction in the line between the condenser and the gauge port, then this explains everything. A restriction would drop the pressure and the temperature.
If I am not mistaken, there is a check valve and orifice in this line, which should provide full flow in cooling mode and metered flow in heating mode. Being in cooling mode it should be providing full flow, therefore there should be no temp drop across it. Check the line temps on either side of it.
mackking
08-06-2009, 03:09 AM
i connected the guages to the taps at the shutoff valves outside the condensing unit. where is this check valve? and is it possible to have 2 units in a row with the same vale bad? also something else that had me concerned is that i had to install 2 90degree elbows at the condensing unit. they are a sweep 90 in the high side line, and they are about 9 inches apart. would this make a difference? my guages are attached to the condenser before the lines. i would think that if there was a restriction in my lines, it would show high pressure, right? i really believe that is just not compressing the refriderant enough to make it flash at 38 degrees. but i dont know why. judging by the way it act , i would agree with you about there being a restriction or a check valve to be faulty, i also find it hard to believe that 2 completly different units can have the same symptoms. so what could remain the same after everything has been changed?
Here is a link for a heat pump installation manual:
http://www.alpinehomeair.com/related/Goodman%20Heat%20Pump%20-%20Install%20and%20Operating%20Inst.pdf
Check out the piping diagrams on page 10. Note the liquid line has a check valve/orifice at each end near the bottom of each coil, with the service valve in between.
mackking
08-06-2009, 03:55 AM
thank you for the link, that is the exact manual for my unit(lol). i see the check valves you are refering to, and its also the expansion valves, i know for a fact that the valve in the air handler is fine and workin properly, the one in the condensing unit is another story but i really dont have any reason to distrust it being as its new and i have the same issue as the old one. ive even been as far as to check the voltages to make sure it wasnt low and causing it to run slow but thats kinda how it acts, like its just not pumping enough.
mackking
08-06-2009, 03:58 AM
how much differential (between high side and low side) does r22 need to flash at the correct temp?
how much differential (between high side and low side) does r22 need to flash at the correct temp?
Sorry, but I don't understand the question.
mackking
08-06-2009, 04:08 AM
i also understood the the purpose of the condensing coil was to cool the refriderant and tranform it from a gas to a liquid but allow it to stay at a high pressure state. by this understanding, u pressurize the refriderant(causing heat) but then the heat is removed by the coil so u have u high pressure cool liquid, right? but it seems the compressor isnt making enough pressure to cause any heat, like i said before, there is very little heat coming out of the condenser even in the heat of the day. also seeing that u are in port richey u know how hot is been lately, and im only about and hour and a half from u. ive never seen anything like it.
mackking
08-06-2009, 04:11 AM
if u have a low side pressure of 70psi.
witch is the pressure in witch the r22 is supposed to flash at around 38 degrees, is there a certain high side required to make this happen?
In your original post you said that the indoor unit came with a .073 orifice and the outdoor unit came with a .078 orifice. Perhaps you were supposed to install them?
mackking
08-06-2009, 04:16 AM
say for example, i have a high side pressure of 165 psi, and a low side pressure of 70 psi, that make a differential of 95 psi. so that means there is 95 psi of liquid pressure on the expansion valve and goin through it. is that enough? in my past its usually a diffence of about 170 psi.
mackking
08-06-2009, 04:21 AM
i assumed that the orifice that came with the condenser was for the evaporater, and i assumed this because the unit was factory charged and it would have meant evacuating the system to install it in the condenser. the one that came with the evaporater was installed so i really dont know
if u have a low side pressure of 70psi.
witch is the pressure in witch the r22 is supposed to flash at around 38 degrees, is there a certain high side required to make this happen?
The saturation temp of R22 at 70psi is 41F. Flashing is the process by which the entering liquid cools down to saturation temp. It has nothing to do with pressure differential.
i assumed that the orifice that came with the condenser was for the evaporater, and i assumed this because the unit was factory charged and it would have meant evacuating the system to install it in the condenser. the one that came with the evaporater was installed so i really dont know
Check the line temps entering and leaving the outdoor check/orifice. If there is a temp difference, you have found your problem.
mackking
08-06-2009, 04:33 AM
ill try it. now you are refering ti the heatpump orifice, right? did u understand what i was aking about the differential pressures?
i assumed that the orifice that came with the condenser was for the evaporater, and i assumed this because the unit was factory charged and it would have meant evacuating the system to install it in the condenser.
It ain't necessarily so. In heat mode the indoor coil is the condenser and the outdoor coil is the evaporator. Put it in heat mode and close the liquid line valve. This pumps the system down with the bulk of the charge in the condenser (indoor coil).
ill try it. now you are refering ti the heatpump orifice, right? did u understand what i was aking about the differential pressures?
I am referring to the check/orifice located in the outdoor unit.
Differential pressure has nothing to do with flashing or saturation.
While you are in there, hook up a gauge to the discharge line access port near the compressor. This will tell you what the condenser pressure really is.
If the discharge pressure is considerably higher than the liquid pressure, this would positively confirm the restriction.
also seeing that u are in port richey u know how hot is been lately, and im only about and hour and a half from u. ive never seen anything like it.
Bite your tongue. I'm in New port richey.
Being from Michigan, I love the heat. It's like... a vacation in Florida.
If you don't have to shovel it out of the driveway... it's all good.
mackking
04-07-2009, 06:05 AM
mr gary, i took the system apart today, i found nothing wrong. the only thing i found is the filter/dryer on the liquid line seemed to have some restriction, so i replaced to- to no avail. i understand that when r22 is compressed through an orfice and enters a 70psi condition, is supposed to flash at 40degrees. if i place my temp probe just beyond the indoor orfice to the lines (with the probe wrapped in insulation tape to the line) i get a temp of 54 degrees. why is this? i dont understand why the refrigerant isnt flashing at the correct temp. what could possibly cause it? like i said before, i am an amature but i have never had this much trouble and i can usually figure it out but im stumped.
james770
04-07-2009, 08:12 AM
Could it be possibly that the compressor internal suction reed is leaking and giving you wrong pressure readings.Maybe pumpdown the system and see if the reeds hold the pressure
Did you find the check/orifice in the outdoor unit?
Did you hook up a gauge to the discharge line access?
mr gary, i took the system apart today, i found nothing wrong. the only thing i found is the filter/dryer on the liquid line seemed to have some restriction, so i replaced to- to no avail. i understand that when r22 is compressed through an orfice and enters a 70psi condition, is supposed to flash at 40degrees. if i place my temp probe just beyond the indoor orfice to the lines (with the probe wrapped in insulation tape to the line) i get a temp of 54 degrees. why is this? i dont understand why the refrigerant isnt flashing at the correct temp. what could possibly cause it? like i said before, i am an amature but i have never had this much trouble and i can usually figure it out but im stumped.
The system doesn't work the way you think it should work, because the way you think it works is WRONG.
Okay... let's try this again:
I would start with the .078 orifice, and measure the air in/air out temps for both coils (temps close to the coils, not way out at the vents), the low and high side pressures, and the suction line (compressor inlet) and liquid line (condenser outlet) temps.
The temp at the thermostat would also be useful.
What I'm looking for here is a set of real measurements, not ranges, guesses and opinions.
mackking
04-07-2009, 05:48 PM
ok tell me exactly what temps you want to know and where also keep in mind the temps change by time times if day. i use u mulitimeter with a temp probe. i also found the outside orfice to be in correctly and free (its a .55)
mackking
04-07-2009, 05:52 PM
should the refrigerant passing through the orfice make a constant hissing sound or would it sound erratic?
Evap air in temp
Evap air out temp
Low side pressure
Suction line temp at outdoor unit
Cond air in temp
Cond air out temp
High side pressure
Liquid line temp at outdoor unit
Discharge line pressure would also be helpful here.
What I am looking for is a snapshot of how the system is performing, so all of the measurements should be taken within a reasonably short period of time.
i understand that when r22 is compressed through an orfice and enters a 70psi condition, is supposed to flash at 40degrees. if i place my temp probe just beyond the indoor orfice to the lines (with the probe wrapped in insulation tape to the line) i get a temp of 54 degrees. why is this? i dont understand why the refrigerant isnt flashing at the correct temp. what could possibly cause it?
High temp liquid exits the metering device and then flashes off to reduce its temp to saturation. The temp in between can be anywhere in between. The correct temp at this point is "whatever it needs to be". So... measuring the flash temp tells you absolutely nothing useful.
mackking
05-07-2009, 05:32 AM
ok the stat says 76 room temp
evap-air in 76
air out 65
condensor- air in 79
air out 88
suction line temp 72
liquid line 89
low side pressure= 66 psi
high side pressure=170 psi
the low side pressure reading was taken from the direct low tap at the compressor(wich is the same pressure as the shutoff taps)
i hope these measurments are the ones you need and thanks for all your help
Was the high side pressure taken at the direct high side tap at the compressor? I'm wondering if it is the same pressure as the high side shutoff tap.
mackking
05-07-2009, 06:55 AM
these readings were taken at 11 pm which is why the low side pressure is less than 70 psi, the day it reaches 70, which is what i charged it to.
mackking
05-07-2009, 06:56 AM
there is no other high side tap
mackking
05-07-2009, 07:00 AM
there is no other tap in the high side
Ok... then we have no choice but to trust the high side pressure measurement at the shutoff tap.
ok the stat says 76 room temp
evap-air in 76
air out 65
condensor- air in 79
air out 88
suction line temp 72
liquid line 89
low side pressure= 66 psi
high side pressure=170 psi
suction line temp is 72F
saturated suction temp for R22 @ 66 psi is 38F
72 - 38 = 34F superheat
Add refrigerant slowly until the superheat is about 15F, then take a new full set of temp and pressure readings.
tonyelian
05-07-2009, 07:58 PM
hi
is the unit is enough for the area coverd more detail pls
size of both orifices &u fitted with o ring&right direction
did condensing unit match air handling
more detail pls
mackking
06-07-2009, 03:01 AM
suction line= 56f
liquid line=93f
low side=85psi
high side=200psi
condensor air in=82f
condensor air out=94
evap air in=77f
evap air out=59f
mackking
06-07-2009, 03:05 AM
its a 3 ton goodman heat pump with matching air handler (both brand new).
its in a 900sq ft mobile home (with a lot if insulation).
the indoor orfice is a .82 and the outdoor orfice is a .55
both are in correctly and workin correctly
The .082 orifice is too large and is overloading the system. You need to switch to the .078 and then take a new set of readings.
mackking
06-07-2009, 03:55 AM
i know the orfice is too large but when i put the .78 in, the vent temp rose 8f
We need to get everything in balance. And at this point the orifice is too large.
mackking
06-07-2009, 04:06 AM
ok ill put it back in but how will i get the temp down
how cold can i make it get?
mackking
06-07-2009, 04:09 AM
am i expecting too much from this unit? because i really expected to see temps in the 40's.
mackking
06-07-2009, 04:21 AM
it would seem that my understanding of how the system works is wrong, so what directly determinds how cold the coil gets?
Planning on turning your mobile home into a refrigerator?
Once we get the system in balance the next step will be to reduce the blower speed.
mackking
06-07-2009, 04:36 AM
well kinda, i just want it to cycle during the day instead of running all the time. i keep the stat set on 70f, during the day it get up to about 82 of 83. when night falls, it takes it until 2am to bring it back down to 70.
i would have said that it was an insulation problem, but i rebuilt the house last year and completely packed every wall with styrofoam and fiberglass insulation then sealed the outside with thermoply before putting the siding back on. also if it were an insulation problem, i would figure it would recover fast at night or during the rain but it dont. and im trying to reduce my light bill from $400.
well kinda, i just want it to cycle during the day instead of running all the time. i keep the stat set on 70f, during the day it get up to about 82 of 83. when night falls, it takes it until 2am to bring it back down to 70.
i would have said that it was an insulation problem, but i rebuilt the house last year and completely packed every wall with styrofoam and fiberglass insulation then sealed the outside with thermoply before putting the siding back on. also if it were an insulation problem, i would figure it would recover fast at night or during the rain but it dont. and im trying to reduce my light bill from $400.
I have 3 tons for 1500 sq ft and it pulls down pretty fast. For 900 sq ft it should pull down very fast... but first we need to get it working right.
mackking
06-07-2009, 04:52 AM
i couldnt agree more. ive never had this much trouble. ive always just charged a system to 72psi on the low side and it worked but like i said i havent done a whole lot of it.
i couldnt agree more. ive never had this much trouble. ive always just charged a system to 72psi on the low side and it worked but like i said i havent done a whole lot of it.
I've heard of a lot of different ways to charge a system, but that is probably the worst.
BTW, right now you have 6F superheat, which means the system is overcharged. I clearly remember saying charge it to 15F superheat.
mackking
06-07-2009, 05:19 AM
well maybe before this is all said and done, ill know the correct way. its sure been a learning experiance.
You might want to read through this thread:
http://www.refrigeration-engineer.com/forums/showthread.php?t=19701
tonyelian
06-07-2009, 08:27 PM
hi
ur orifice size should be 065 indoor&o70 outside
mackking
07-07-2009, 02:06 AM
ok i put the .78 back in and reset it and set the evap blower to low(from medium)
suction line=62f
liquid line=88f
lowside=80psi
highside=190psi
condensor in=79f
condensor out=89f
evap in=76f
evap out=60f
mackking
07-07-2009, 02:13 AM
the .78 came with the air handler and the .58 was factory installed in the condensor. from all the experiments ive tried, when i install a smaller orifice, the vent temp rises. my only explination is that when i install a smaller orifice, it restricts the refrigerant flow too much and cant keep up with the coil. but i could be wrong.
With suction pressure that high the discharge pressure should be much higher. I'm thinking you may have an inefficient compressor.
Close the suction line shutoff valve and see if the compressor will pump down into a vacuum.
mackking
07-07-2009, 03:25 AM
what would cause the compressor to be inefficient? and what would cause two of them to be? like i said before, this is the second system and both of them act the exact same way. i have examined both refrigerant lines inside and out and both are fine and restriction free.
mackking
07-07-2009, 03:50 AM
um not very well. it pulled it to a 8inhg vacuum. is that enough? or could it be the reversing valve leaking? i have questioned the reversing valve all along but i dont know how to check it.
it doesnt seem to have much efficientcy in heat mode either but that could be a compressor too, right?
I found a piston kit chart. Let's see if we can find the official right size:
http://site.famousparts.com/goodman/PDF/PKC-00U.pdf
mackking
07-07-2009, 04:15 AM
the condensor is a model # gsh130361bb
the air handler is a model#
adpf304216ba
i couldnt find the exact app for this unit in the charts.
mackking
07-07-2009, 04:31 AM
oh i dont know if it matters, but whan i closed the suction shut-off valve, the high side pressure DID NOT rise.
Is there a model# on the coil?
oh i dont know if it matters, but whan i closed the suction shut-off valve, the high side pressure DID NOT rise.
Did the low side pressure at the compressor inlet go into a vacuum?
mackking
07-07-2009, 04:35 AM
which coil? but probly not there is not alot of id numbers on it
mackking
07-07-2009, 04:36 AM
not much of a vacuum, 8 inhg
which coil? but probly not there is not alot of id numbers on it
The indoor coil.
the condensor is a model # gsh130361bb
the air handler is a model#
adpf304216ba
i couldnt find the exact app for this unit in the charts.
The ADPF304216BA can have a 2.5 to 3.5 ton coil.
As near as I can tell a 2.5 ton needs .065 and a 3.5 ton needs .078
mackking
07-07-2009, 05:24 AM
i cant find any other numbers, so what do u think about the vacuum and pressure?
mackking
07-07-2009, 05:27 AM
i was told that the air handler was built to range from a 2 1/2 ton -3 1/2 ton, making it a good candiate for my 3 ton condensor
I am not ready to blame the compressor just yet. We need to get the right orifice in there and see what the temps/pressures tell us.
The .078 is just too large, so we can assume that the coil is not 3 1/2 ton.
Unless you can find the btu rating for the coil we will just have to keep changing orifices.
I want to see that suction pressure down around 70 psi (or a little less) with about 15F coil outlet superheat.
mackking
07-07-2009, 11:41 PM
well before i knew about the superheat method, i was setting the suction pressure at 70psi or little below, and when i put in smaller orifices(trying to raise the head pressure) i would loose a significant amont of efientcy. wich is how i ended up with the .82 orfice, the gave me the coldest vent temp.
it still really concerns me, that when i shut off the suction valve completly, the high side didnt change but the low side came down to a small vacuum. before i blamed the compressor, i would question the reversing valve, but i dont know how to check it.
You keerp mentioning the vent temp as if it were important.
mackking
08-07-2009, 12:43 AM
if it dont blow cold then whats the point?
mackking
08-07-2009, 12:44 AM
60f just isnt cold
if it dont blow cold then whats the point?
The point is transferring heat.
mackking
08-07-2009, 02:29 AM
call it whatever you like but the whole fact of the matter is that it cant transfer heat if it cant make heat, and with a head pressure of 180psi, it cant make heat. and when i close off the suction line and it still dont raise the head pressure, nothing will no matter how many orifices i throw at it.
call it whatever you like but the whole fact of the matter is that it cant transfer heat if it cant make heat, and with a head pressure of 180psi, it cant make heat. and when i close off the suction line and it still dont raise the head pressure, nothing will no matter how many orifices i throw at it.
Why would you expect the head pressure to rise when you shut off the suction valve?
Did you try another orifice today?
mackking
08-07-2009, 03:27 AM
no i didnt have a chance, but i would expect the pressure to rise since the refrigerant has nowhere to go, it would be compressed in the coil, hense the pressure should skyrocket.
mackking
08-07-2009, 03:31 AM
the only other orifice i have is a .73, but when i installed it before it acted like it had too much restriction to flood the coil with enough refrigerant to keep it cool.
no i didnt have a chance, but i would expect the pressure to rise since the refrigerant has nowhere to go, it would be compressed in the coil, hense the pressure should skyrocket.
When you shut off the suction the compressor has nothing to pump into the high side... and the high side is still cooling off and draining off into the evaporator. If anything the high side pressure should drop.
the only other orifice i have is a .73, but when i installed it before it acted like it had too much restriction to flood the coil with enough refrigerant to keep it cool.
Trust me, it will provide enough flow.
mackking
08-07-2009, 05:00 AM
at this point i have nothin to loose so ill try the .73 again
tonyelian
08-07-2009, 07:51 PM
hi
ithink there is miss matching btw the comp&air handler unit it appear that u have a large air hanling unit condenser came with this small orifice should b too small to handle the load u can check the comp brand & serial #
hi
ithink there is miss matching btw the comp&air handler unit it appear that u have a large air hanling unit condenser came with this small orifice should b too small to handle the load u can check the comp brand & serial #
I tend to agree about the mismatch. The evap seems oversized for the compressor, but then this could be simply an orifice mismatch.
More worrisome is that the condenser seems oversized for the compressor.
If the compressor is undersized (under-capacity) for both the evap and the cond, that probably means the compressor is inefficient.
At this point I'm still hoping that the right sized orifice will show a good condenser load, but that may be just wishful thinking.
As mackking says, at this point there is nothing to lose by trying another orifice.
mackking
09-07-2009, 03:46 AM
i put in the .73, set it to 15f superheat but i still have a high pressure on the low side (85psi with a 66f suction line)
the high side psi did rise but only to 225 psi. i couldnt get any more readings because it started pouring on me, but its still not bring the room temp down.
mackking
09-07-2009, 03:52 AM
are u telling me that u think goodman installed the wrong compressor from the factory?
i put in the .73, set it to 15f superheat but i still have a high pressure on the low side (85psi with a 66f suction line)
the high side psi did rise but only to 225 psi. i couldnt get any more readings because it started pouring on me, but its still not bring the room temp down.
Any idea what the indoor and outdoor temps were at the time you took those readings?
are u telling me that u think goodman installed the wrong compressor from the factory?
No... an inefficient compressor is one with broken valves. The symptoms are the same as having an undersized compressor.
mackking
09-07-2009, 04:14 AM
yeah the air in evap was 79 and the air out was 62, i know there is a good difference but it still dont seem cold enough to me.
mackking
09-07-2009, 04:16 AM
how would i confirm an inefficient compressor
yeah the air in evap was 79 and the air out was 62, i know there is a good difference but it still dont seem cold enough to me.
And what was the outdoor temp?
mackking
09-07-2009, 04:27 AM
i couldnt check it at the time because of the rain but i thinkit was around 85
As the temp in the house comes down the superheat will drop, so you should remove some refrigerant to keep it up around 15F.
i couldnt check it at the time because of the rain but i thinkit was around 85
225 psi at 85F would be an improvement. There may be hope for this system yet.
mackking
09-07-2009, 04:40 AM
there may be hope but it hasnt brought it down and shut off yet, do u think this is any indication of how its gonna perform?
tbirdtbird
09-07-2009, 04:40 AM
I have to wonder if pix would help. There may be a surprise in store. It has happened with other threads.
mackking
09-07-2009, 04:41 AM
what kind of pics do u want?
there may be hope but it hasnt brought it down and shut off yet, do u think this is any indication of how its gonna perform?
To get the charge just right, you need to adjust to 15F superheat when the house is down to your shutoff temp. We've been just ballparking it to compare orifices.
mackking
09-07-2009, 05:00 AM
is the superheat effected by night time or daytime?
mackking
09-07-2009, 05:00 AM
it just shut off!!
mackking
09-07-2009, 05:02 AM
from 830 to 12 to drop it 8f
When it comes back on would be the best time to adjust the charge.
mackking
09-07-2009, 05:14 AM
will the superheat skyrocket during the heat of the day? or should it stay pretty much the same?
will the superheat skyrocket during the heat of the day? or should it stay pretty much the same?
The superheat will be higher when the house is warm.
from 830 to 12 to drop it 8f
You are not only cooling the air in your house... you are cooling everything in your house. And you are also dehumidifying everything. It has been very humid lately.
mackking
09-07-2009, 05:47 AM
yeah i know
mackking
09-07-2009, 10:46 PM
so far its holding 70f in the room, but it has been overcast and raining today too. so far so good
Got a full list of temps/pressures?
mackking
09-07-2009, 11:16 PM
nope still rainin, but its running about 35-45 minutes during cycles
Did you trim the charge to 15F superheat?
mackking
10-07-2009, 03:03 AM
i got in contact with goodman tesh support, they said the system required a .73 orifice(which i installed) and a superheat of 22f because uf the humidity. i did this yesterday and it has worked the best today but like i said it was overcast and raining. anyways here are the reading-
suction temp=62f
liquid line=83f
condensor in=77f
condensor out=88
evap in=66
evap out=53
lowside=72psi
highside=175psi
mackking
10-07-2009, 03:04 AM
this was taken at 10pm and it was wet, 95% relative humidity
Low delta-T's... high suction... low head... I'm thinking this compressor is inefficient.
The only other possibility would be a leaking reversing valve, but you checked the suction pressure on both sides of the reversing valve and they were identical.
I found a Goodman service manual:
http://www.hvacpartsshop.com/asc%20series.pdf
tonyelian
10-07-2009, 08:36 PM
hi
ur air handler is 3.5 tons&condenser is 3 tons there is a miss match
gary tanks for the link&the way u guide him
i think every thing is clear now
The air handler is rated at 2.5 to 3.5 tons, based on 400CFM per ton. It is currently set on low speed (1000CFM) which should result in a low suction pressure... but the suction pressure is in fact high.
One more thing we can try is to measure the temps of the two cold pipes at the reversing valve. If the valve is leaking across, the temp on the side towards the compressor will be considerably higher.
mackking
11-07-2009, 02:58 AM
would a leaking reversing valve of an inefficient conpressor still pull a vacuum when the suction line is closed?
mackking
11-07-2009, 03:00 AM
you asked if it would pull a vacuum, it did but it didnt do it fast and it wasnt much. ive seen systems with a clogged orifice and they would pull a hard hacuum very quickly.
mackking
11-07-2009, 03:03 AM
also as a bit of info, the tech at goodman said he didnt think the highside pressure was low. but as im learning more of how the system works, it seems it would need a higher pressure to keep the refriderant from boiling in the liquid line, right?
Where are you measuring the evap air in and air out temps? Best would be at the air handler.
mackking
11-07-2009, 03:35 AM
the return air is right above the air handler about 1ft and the closest out is at a vent 3ft away. its a downdraft.
mackking
11-07-2009, 03:40 AM
i cant measure the out temp right from air handler because it mounts to the floor so i have to use the closest vent
3 ft away should be accurate.
it seems it would need a higher pressure to keep the refriderant from boiling in the liquid line, right?
Uhhh... No.
also as a bit of info, the tech at goodman said he didnt think the highside pressure was low.
I would disagree. Generally the SCT is 20-35F above the temp of the air entering the condenser (20-35F TD), depending upon load and relative coil size. I have yet to see the TD hit 20F despite the high suction pressure.
mackking
11-07-2009, 06:08 AM
Uhhh... No.
in reading your post in a/c 101, you explained that the boilding of refrigerant in the evaporator removes the heat from the air(which i understand) but i also understood it to say by raising the pressure in the condensing coil it returned the refrigerant back to a liquid(by increasing pressure and removing the added heat) so i guess my question is, is the system raising the pressure enough to maintain the proper liquid state?
mackking
11-07-2009, 06:16 AM
my next question is, by overcharging and having the wrong orifice, could that have damaged the valves in the compressor?
in reading your post in a/c 101, you explained that the boilding of refrigerant in the evaporator removes the heat from the air(which i understand) but i also understood it to say by raising the pressure in the condensing coil it returned the refrigerant back to a liquid(by increasing pressure and removing the added heat) so i guess my question is, is the system raising the pressure enough to maintain the proper liquid state?
R22 at 175psi gives you a saturated condensing temp (SCT) of 93F. In order for the liquid in the liquid line to boil off, its temp would have to be higher than 93F. Its temp is 83F. Not going to happen... and since the two temps go up and down together, it can't happen.
:mad:
my next question is, by overcharging and having the wrong orifice, could that have damaged the valves in the compressor?
Yes... it could.
Did you measure the temps of the suction lines entering and leaving the reversing valve?
Richvacr
11-07-2009, 02:07 PM
it sounds like you are closer to getting it. if not what I would do is recovery the refrigerant, return both units to goodman specs, evacuate according to goodman instructions. Then weigh in the factory charge and weigh the additional charge according to what Goodman says - for example .68 oz or each additional foot beyond 15 feet. I have seen it stated to recovery refrigerant for less then 15 feet also.
If this does not give you a good operating ac then call goodman and say what the ....
Richvacr
11-07-2009, 02:14 PM
The other thing is where is the expansion valve? I do not have much experience with Goodman but it seems all manufactures have gone with txvs since the high SEER. Could you have a 13SEER Cond and a 10SEER Evap coil?
A txv might work better anyhow
mackking
11-07-2009, 03:43 PM
the epansion orifice is in the front of the case. i am pretty sure its a 13seer handler too. and as far as it having a txv, the handler i removed had a txv and i didnt like it. i would prefer to have an orifice simply because its just less to question its functionality.
Richvacr
11-07-2009, 05:25 PM
to me a txv is much easier. I've always had good luck with weighing in a charge - estimating distance if I did not install the lineset. Check subcooling and everything works out.
Since the txv meters the refrigerant by suction temp I'd think you get better performance.
As for fouling the txv it is just as likely to plug the orifice with a dirty lineset.
mackking
11-07-2009, 05:29 PM
this is true. everyone prefers different things, ive just had better luck with orifices.
mackking
12-07-2009, 03:41 AM
i cant see a difference in the temps on the reversing valve. also, when i would pump the system into the condensor to change the orifice, it would hold the pressure in the highside and not bleed back to the lowside, so i think the valve is fine. as for the compressor, im not sure.
Yep... everything points to the compressor.
mackking
12-07-2009, 04:27 AM
is it likely to have 2 compressors, from 2 separate units, built by different companies, be inefficient? i guess thats my doubt.
mackking
12-07-2009, 04:28 AM
one being used but worked when removed other than a leak in the condensing coil(which i fixed) and the other being brand new.
I have no way of knowing what the other unit did or did not do.
mackking
12-07-2009, 04:44 AM
it had the exact pressure characterisitcis, but it was older and i didnt know much about it, other than it ran but had a leak. it did however have a lower head pressure and a higher suction pressure then normal. like the one i have now.
What are the make and model number for your compressor?
mackking
12-07-2009, 04:55 AM
ill have to take it apart to get them, but it is a recipricating compressor.
mackking
12-07-2009, 04:58 AM
i dont know if i told u, but i really appeciate all your help and advice. you have taught me alot in the last week or so
Powered by vBulletin® Version 4.2.1 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.